The Next Step in Malaria Prevention May Be to Make People Taste Bad

Desperate parents of nail-biting kids and furniture-chewing dogs often turn to foul-tasting compounds to deter their loved ones’ gnawing. In the future, we might be trying something similar with mosquitoes, as scientists now say that malaria-causing mosquitoes use scent and taste to decide who to bite. They published their research in the journal Nature Communications.

The mosquito, that scourge of summer, is more than just a nuisance. Mosquito-borne viruses like Zika and dengue are on the rise. Rates of malaria are down, but still high; around 214 million people were affected in 2015 alone. As drug developers race to develop vaccines, other scientists are hoping to find ways to keep disease-carrying mosquitoes from biting in the first place. To do that, they’ve got to know mosquitoes inside and out.

A mosquito lives by its noses. Yes, noses, plural. Every mosquito has three sets of scent-detecting parts: two antennae, two fuzzy mouthparts called maxillary palps, and two little spots called labella at the end of its proboscis. The antennae and palps are scent-only, but the labella contain neurons for sensing both smell and taste.

That’s a lot of olfactory information for a teeny tiny brain to take in. To find out how the mosquitoes do it, researchers tinkered with the genes of the malaria-carrying mosquito Anopheles gambiae. They tricked out the mosquitoes with a gene that would cause cells called odorant receptors (ORs) to glow bright green, which would make them easier to spot under a microscope. Building fluorescent proteins into bug parts is not a new technique, but it’s never been done before in mosquitoes.

This is a female Anopheles gambiae mosquito with olfactory neurons on the antennae, maxillary palp, and labella labeled in green. Image Credit: Olena Riabinina and Courtney Akitake, Johns Hopkins Medicine

By looking at the mosquitoes’ glowing ORs, the team was able to trace the paths from the pests’ sense organs to their brains. They found that information taken in by the antennae and maxillary palps was sent to brain regions called antennal lobes (this process is the same in flies). But signals from the labella went over to an area called the subesophageal zone—an area that had previously only been associated with taste.

The researchers say this likely means that a mosquito not only sniffs us but tastes us, too, poking with the end of its proboscis to confirm we’re edible before unsheathing its gross, syringe-like feeding needles.

It’s an unsettling concept, to be sure, but it might just help us out down the road. Co-author Christopher Potter, a neuroscientist at Johns Hopkins University, says we could use An. gambiae's brain cells against it—all we have to do is convince it that we taste terrible. “Our goal is to let the mosquitoes tell us what smells they find repulsive and use those to keep them from biting us,” he said in a statement.

Lead author Olena Riabinina, now at Imperial College London, noted that their success with the glowing protein has created new possibilities for mosquito research. “We were pleasantly surprised by how well our genetic technique worked and how easy it is now to see the smell-detecting neurons,” she said. “The ease of identification will definitely simplify our task of studying these neurons in the future."

In 2016, a study on mice found that certain sleep traits, like insomnia, have genetic underpinnings. Several studies of human twins have also suggested that insomnia can be an inherited trait. Now, new research published in Molecular Psychiatry not only reinforces that finding, but also suggests that there may be a genetic link between insomnia and some other psychiatric and physical disorders, like depression and type 2 diabetes, as Psych Central alerts us.

Insomnia is particularly prevalent in populations of military veterans. For this study, researchers at VA San Diego Healthcare System analyzed questionnaire responses and blood samples from almost 33,000 new soldiers at the beginning of basic training, along with pre- and post-deployment surveys from nearly 8000 soldiers deployed to Afghanistan starting in early 2012. They conducted genome-wide association tests to determine the heritability of insomnia and links between insomnia and other disorders. The results were adjusted for the presence of major depression (since insomnia is a common symptom of depression).

The genotype data showed that insomnia disorder was highly heritable and pinpointed potential genes that may be involved. The study indicated that there's a strong genetic correlation between insomnia and major depression. (The two were distinct, though, meaning that the insomnia couldn't be totally explained by the depression.) They also found a significant genetic correlation between insomnia and type 2 diabetes.

Because the study relied on data from the U.S. military, the study doesn't have the most far-reaching sample—it was largely male and wasn't as racially diverse as it could have been. (While it analyzed responses from recruits from European, African, and Latino ancestry, there weren't enough Asian-American participants to analyze as a group.) The responses were also self-reported, which isn't always the most accurate data-collection method.

The genes indicated by this study could be used to develop new treatments for insomnia, but future studies will likely need to explore these questions within broader populations.

Have you ever noticed that your fingers and toes get wrinkled when you’ve been soaking in water for a while? We often call this “prune hands,” because it makes your fingers look shriveled like a prune. (A prune is a dried plum.) The shriveling happens when blood vessels under your skin get narrower. This is caused by your autonomic (Aw-toe-NAW-mick) nervous system. Thissystem keeps your lungs breathing and your heart beating without you having to think about it.

The wrinkles seem to help us grip and not slip! Look at the bottom of your shoe. Does it have grooves? Those are called treads. The tires on cars and buses have treads too. The water that goes into those narrow grooves gets pushed away. It works the same way with your skin. Water drains from your hands through these grooves. We think this helps us to hold onto objects better. Scientists tested this theory with an experiment. They asked people with wet, wrinkled hands to pick up wet marbles and dry marbles. People picked up the wet marbles faster with wet, wrinkled hands.

Some scientists now think that humans evolved (Ee-VAWLVD)—changed over time—to have this reaction. Being able to hold onto wet things might have helped our ancient ancestors survive. Think about it: if your food lives in a wet place, like a river, ocean, or rainforest, you have a better chance of grabbing it if your fingers “stick” to it. If you are climbing a wet tree, wrinkled fingers might help keep you from falling. Wrinkled toes can help, too. If you’re barefoot, your toes need a good grip in wet or muddy places.

Want to hear more about the marble experiment? Watch this video from SciShow.